Massachusetts state police say a body part recovered from the Charles River may be part of an animal carcass and not human remains as originally suspected.

State police spokesman David Procopio says the medical examiner will make the final determination.

The remains were found less than two hours after authorities discovered a body around 9 a.m. Saturday floating in the Muddy River. Boston police are investigating that case.

State police originally suspected the remains recovered from the Charles River were possibly related to other human body parts found in the river about a month ago. They stressed that the discovery Saturday did not indicate any ongoing threat to the public.

Lawyers for Boston Marathon bomber Dzkokhar Tsarnaev rested their case in his federal death penalty trial Tuesday after presenting a brief case aimed at showing his late older brother was the mastermind of the 2013 terror attack.